Under the Family Smoking Prevention and Tobacco Control Act, which for first time gave the FDA the authority to regulate tobacco products in 2009, cigarette makers will be forced to cover half of all cigarette packs and 20% of all advertisements with one of nine graphic warning labels selected by the federal agency. The grim images on the labels include depictions of a smoker’s corpse, diseased lungs, and mottled and stained teeth and gums damaged by smoking.

The warning labels are currently hung up in the courts, however. Five tobacco companies are suing the government on the grounds that the new labels — which the companies argue are designed to provoke an emotional response and further the governments’ anti-smoking agenda, rather than simply conveying information to consumers — tread on their First Amendment right to free speech.

In the meantime, a question worth asking: How well do the graphic warning labels actually work? That is, do they help people remember the content of the warning better than text-only labels?

A recent study, led by Andrew Strasser of the University of Pennsylvania School of Medicine, suggests that they do. The study recruited 200 adults — all current smokers who weren’t trying to quit — to view a cigarette ad, with either a text-only tobacco warning label on the bottom (displaying the standard Surgeon General’s warning: “Quitting smoking now greatly reduces serious risks to your health”) or a larger, more arresting graphic label showing a hospitalized man on a ventilator alongside the written message: “Cigarettes cause lung cancer. Every cigarette you smoke increases your chance of getting lung cancer.”

Each version was designed to match the current size standard for text-only warnings or the pending requirements for the FDA‘s graphic labels.

Participants viewed each image for 30 seconds, and then, as a distraction task, answered questions about their general opinions of the ad. Then, the researchers tested how well the viewers could remember what the warning labels actually said. Half of people who saw the ad with the text-only warning label were able to recall its content. But 83% of those viewing the graphic label could accurately remember its message.

“An important first step in evaluating the true efficacy of the warning labels is to demonstrate if smokers can correctly recall its content or message,” said Strasser, an associate professor of psychiatry at Penn, in a statement.

The researchers also used eye-tracking software to determine what parts of the ads engaged participants’ attention and for how long. People looked the graphic warning label significantly longer than the text label (11.1 seconds vs. 8.2 seconds) and were drawn to it much faster, within 1.7 seconds of being shown the ad, versus. 2.5 seconds for those in the text-only condition. Both the duration and speed of participants’ gaze predicted better recall of the warning label’s content.

The authors note that it’s possible that these longtime smokers — who reported smoking an average 16.6 cigarettes a day for 12.8 years — didn’t pay as much attention to the standard Surgeon General’s warning because they were already so familiar with it. “However, this would not explain why they could not recall the text as well as those in the graphic condition,” the authors write in the study, published in the American Journal of Preventive Medicine.

They observe:

Results from the current study demonstrate the effectiveness of graphic warning labels in cigarette advertisements in increasing recall of warning label–based smoking risks and provide novel objective evidence that smokers’ viewing patterns of cigarette advertisements containing graphic warning labels are associated with recall.

Strasser and his colleagues conclude: “Graphic warning labels should be incorporated into cigarette advertisements without delay; not doing so only prolongs an overdue, necessary improvement to U.S. tobacco control.”